Comparative study of semipolar (202¯1), nonpolar (101¯0) and polar (0001) InGaN multi-quantum well structures grown under N- and In-excess by plasma assisted molecular beam epitaxy

InGaN multi-quantum well (MQW) structures were grown by plasma-assisted molecular beam epitaxy (PAMBE) on semipolar (202¯1), nonpolar m-plane (101¯0) and polar c-plane (0001) GaN substrates. The impact of In- and N-rich growth conditions on surface morphology, luminescence properties and structural quality was studied. Semipolar MQWs grown under N-excess have a smooth surface and narrow photoluminescence (PL) at room temperature at 420 nm. Semipolar MQWs grown under In-rich conditions emitted at 414 nm with slightly broader emission and higher surface roughness. Nonpolar m-plane MQWs grown under N-excess emitted at 411 nm and its surface was very rough. When grown under In-rich conditions, nonpolar MQWs also emitted at 411 nm but significant peak broadening was observed due to hillock formation resulting in surface roughening and inhomogeneous In incorporation. The c-plane reference MQW structures grown in the same growth run did not show PL at room temperature due to poor structural quality related to three-dimensional growth mode and structure relaxation.